A.02 Recent Literature. [Ju'y 



red condition of the pouch might easily be explained by individual or 

 accidental causes. As Brown Pelicans are found on both sides of the 

 Panama Isthmus, and must fly across it, a comparison of Central Ameri- 

 can specimens should furnish important points on this subject. As now 

 stated, the West Coast bird looks like a mere subspecies or local race. 



Cymochorea melania and C. hoirochroa. — Notwithstanding Mr. Ridg- 

 wav's positiveness, I have to reassert the facts regarding Emerson's 

 specimens, that with Ridgway's descriptions before me, and the bird in my 

 hand, I found it to differ from both as mentioned, being decidedly inter- 

 mediate. 



Puffinus Strickland! Ridg. — Mr. Ridgway hinxself answers his question 

 why I considered my specimen P. stricklandi instead of P. griscus, by 

 acknowledging his own error in regard to the difference in size of the 

 two sf-ecies, my bird being larger than the largest size given for the 

 former. Not having the specimen at hand I cannot decide as to plumage, 

 but at the time I collected it I compared it with Coues's monograph of 

 Piifiinus, and found it agree with P. ''f/iligiitosus" {=s.tricklandi) , «o/with 

 P. (^Ncctris) amaurosojna {^griseus). So the question rests on the ac- 

 curacy of the descriptions of Coues and Ridgway. 



As to the unification of several so-called 'species,' we need only to look 

 at the synonymy of most of the Longipennes and Tubinares to see that 

 (Treat combinations of nominal species have been made already, and a 

 study of the species still recognized shows that many of them differ very 

 slicfhtly. Their distinctness is based on the fact that intermediate forms 

 have not yet been found. This is an artificial rather than a natural basis 

 of distinction, as shown by the difference in degree of distinctness found 

 in o'roups of species breeding on continents and tliose breeding on 

 islands; both land and water-birds. In continental groups we find many 

 species embracing several subspecies or geographical races, especially 

 where of very wide range, these races connected by graded links. Island- 

 breeding birds, however, while presenting many local races, are so separ- 

 ated by water from each other that there is no intermediate ground for 

 the production of connecting links, and the local races, therefore, are 

 called 'species' though often less different than the extreme races of some 

 continental birds. Therefore, I still assert that consistency requires the 

 combination of many so-called species of water-birds if not into few^er 

 'species,' at least into groups nearly corresponding to some continental 

 species. The descriptions of the four Puffijii mentioned show close simi- 

 larity in size and form. The difference in plumage, on which two have 

 been separated as Ncctris, if positively proved not to depend on age 

 (which is left unsettled in the 'Water Birds'), may be dichromatic forms, 

 like those of some Herons. There is not enough known yet regarding 

 these birds to decide this question. But accepting Mr. Ridgway's decision 

 that all the species he gives are distinct, we are forced to the conclusion 

 that a 'species' depends rather on the nature of the earth's surface, separ- 

 ating the breeding places of two forms, than on the degree of difference 

 between the forms themselves. — ^J. G. Cooper, M. D. 



